The invention relates to radio-frequency identification (RFID) sensing devices, and more particularly to inductor-capacitor-resistor (LCR) sensing devices having enhanced selectivity and sensitivity.
Selectivity of sensors is one of critical aspects in sensor performance and applications. Typically, lack of selectivity prevents the wide use of sensors in sensing chemical and biological species in liquids and air for industrial and other applications. Two known approaches to address this problem include (1) developing very selective sensing films and (2) combining individual diverse sensors into an array. Unfortunately, each approach suffers from its own limitations. Highly selective sensing films typically have relatively slow recovery times due to strong vapor-material interactions. Combining sensors into an array could have manufacturing challenges.
Chemical and biological detection has been accomplished using RFID sensors. In this approach, ubiquitous and cost-effective passive RFID tags with integrated circuit read/write memory chips operating, for example at 13.56 MHz, may be adapted for chemical sensing. By applying a sensing film onto the resonant antenna of the RFID sensor and measuring the complex impedance of the RFID resonant antenna it is possible to correlate impedance response to chemical properties of interest. The digital data may also written into and read from the integrated circuit (IC) memory chip of the RFID sensor. This IC memory chip may store a unique digital ID, sensor calibrations, and information about the object onto which the sensor is attached.
Sensor response originates from changes in dielectric properties of the sensing film deposited onto a sensor. While RFID sensors can detect individual chemical and physical changes based on changes in dielectric properties, the selectivity of these sensors may be improved further if other modes of detection are identified.
Therefore, it would be desirable to provide sensor assembly with additional modes of sensing.